124 lines
4.2 KiB
Rust
124 lines
4.2 KiB
Rust
//
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// Copyright (c) 2020 KAMADA Ken'ichi.
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions
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// are met:
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// 1. Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// 2. Redistributions in binary form must reproduce the above copyright
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// notice, this list of conditions and the following disclaimer in the
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// documentation and/or other materials provided with the distribution.
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//
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// THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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// ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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// OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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// OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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// SUCH DAMAGE.
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//
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use std::io::{BufRead, ErrorKind};
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use crate::endian::{Endian, BigEndian};
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use crate::error::Error;
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use crate::util::{BufReadExt as _, ReadExt as _};
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// PNG file signature [PNG12 12.12].
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const PNG_SIG: [u8; 8] = *b"\x89PNG\x0d\x0a\x1a\x0a";
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// The four-byte chunk type for Exif data.
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const EXIF_CHUNK_TYPE: [u8; 4] = *b"eXIf";
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// Get the contents of the eXIf chunk from a PNG file.
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pub fn get_exif_attr<R>(reader: &mut R)
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-> Result<Vec<u8>, Error> where R: BufRead {
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match get_exif_attr_sub(reader) {
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Err(Error::Io(ref e)) if e.kind() == ErrorKind::UnexpectedEof =>
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Err(Error::InvalidFormat("Broken PNG file")),
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r => r,
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}
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}
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// The location of the eXIf chunk is restricted [PNGEXT150 3.7], but this
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// reader is liberal about it.
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fn get_exif_attr_sub<R>(reader: &mut R)
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-> Result<Vec<u8>, Error> where R: BufRead {
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let mut sig = [0u8; 8];
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reader.read_exact(&mut sig)?;
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if sig != PNG_SIG {
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return Err(Error::InvalidFormat("Not a PNG file"));
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}
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// Scan the series of chunks.
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loop {
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if reader.is_eof()? {
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return Err(Error::NotFound("PNG"));
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}
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let mut lenbuf = [0; 4];
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reader.read_exact(&mut lenbuf)?;
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let len = BigEndian::loadu32(&lenbuf, 0) as usize;
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let mut ctype = [0u8; 4];
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reader.read_exact(&mut ctype)?;
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if ctype == EXIF_CHUNK_TYPE {
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let mut data = Vec::new();
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reader.read_exact_len(&mut data, len)?;
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return Ok(data);
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}
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// Chunk data and CRC.
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reader.discard_exact(len.checked_add(4).ok_or(
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Error::InvalidFormat("Invalid chunk length"))?)?;
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}
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}
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pub fn is_png(buf: &[u8]) -> bool {
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buf.starts_with(&PNG_SIG)
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn truncated() {
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let sets: &[&[u8]] = &[
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b"",
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b"\x89",
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b"\x89PNG\x0d\x0a\x1a",
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];
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for &data in sets {
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assert_err_pat!(get_exif_attr(&mut &data[..]),
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Error::InvalidFormat("Broken PNG file"));
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}
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let mut data = b"\x89PNG\x0d\x0a\x1a\x0a\0\0\0\x04eXIfExif".to_vec();
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assert_eq!(get_exif_attr(&mut &data[..]).unwrap(), b"Exif");
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while let Some(_) = data.pop() {
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get_exif_attr(&mut &data[..]).unwrap_err();
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}
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}
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#[test]
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fn no_exif() {
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let data = b"\x89PNG\x0d\x0a\x1a\x0a";
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assert_err_pat!(get_exif_attr(&mut &data[..]),
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Error::NotFound(_));
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}
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#[test]
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fn empty() {
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let data = b"\x89PNG\x0d\x0a\x1a\x0a\0\0\0\0eXIfCRC_";
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assert_ok!(get_exif_attr(&mut &data[..]), []);
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}
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#[test]
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fn non_empty() {
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let data = b"\x89PNG\x0d\x0a\x1a\x0a\0\0\0\x02eXIf\xbe\xadCRC_";
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assert_ok!(get_exif_attr(&mut &data[..]), [0xbe, 0xad]);
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}
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}
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